As the aerospace industry moves into the more electric era, inverter controlled dynamoelectric machine drives become more common onboard aircraft. Next generation dynamoelectric machine controllers must meet many new system and design challenges including cost reduction and reliability improvement. Shaft sensorless dynamoelectric machine control holds great promise for meeting these challenges.
An aircraft generator is usable as a motor for engine starting when powered by an inverter. To reduce cost and improve reliability, it is very desirable to eliminate the mechanical shaft sensor for the engine starter. A novel sensorless synchronous dynamoelectric machine control based on dynamoelectric machine flux estimation, designated Extended Flux Sensorless (EFS) position sensing, is disclosed in U.S. Pat. No. 7,072,790 to Markunas et al. and hereby incorporated by reference. Markunas et al. defines extended rotor flux, which aligns with the rotor field flux axis. The dynamoelectric machine rotor position and speed are estimated from the extended rotor flux, which is derived from dynamoelectric machine terminal electrical potential and current measurements (FIG. 1), expressed in the α-β two-axis stationary reference frame well known in the electric machine technical community. Ideally, a pure integrator is required to reconstruct the flux. However, in practice, a pure integrator suffers from direct current (DC) drifting, initial value holding, and even stability problems. Markunas et al. proposes to alleviate these problems with a lag approximation to an integrator. A digital phase lock loop (FIG. 2) determines the rotor position and speed from the extended rotor flux. The lag approximation to a pure integrator becomes better at high rotor speeds, asymptotically approaching the characteristics of the integrator at very high speeds. However, at low dynamoelectric machine speeds or equivalently low synchronous electrical frequency, ωe, the error due to the lag approximation can become unacceptably large.